The opposition-held city of Idlib could become the next Aleppo in Syria, UN officials warned on Thursday.

The UN’s Special Envoy for Syria Staffan de Mistura made the warning during a joint press conference with Special Adviser Jan Egeland in Geneva.

De Mistura noted that at least 35,000 people have been evacuated so far from eastern Aleppo to mainly Idlib. "Many have gone to Idlib which could be in theory be the next Aleppo," he said.

He underlined that the immediate priority was a cessation of hostilities in Syria.

He also spoke about the worsening weather situation, saying snow was now falling in Aleppo, which in turn was increasing humanitarian needs.

"To date, the UN has 31 staff tasked with monitoring the evacuation from east Aleppo, with another 90 to 100 staff in the city providing additional assistance," he said.

Under the terms of an earlier agreement between the Bashar al-Assad regime and Syrian opposition groups, civilians trapped in eastern Aleppo would be allowed to go to the opposition-held city of Idlib.

Situated near the border with Turkey, Idlib is located some 65 kilometers (40 miles) from Aleppo.

Russia, Turkey and Iran agreed on a "joint declaration" on Tuesday to find a solution in Syria to ensure the evacuation of civilians, including armed groups from eastern Aleppo and the leaders were ready to help broker a Syrian peace deal.

De Mistura praised the agreement and the effort by Turkey and Russia for the Aleppo evacuation and welcomed the joint initiative by the three regional powers for talks in the Kazakh capital of Astana, ahead of UN peace talks that will be convened in Geneva from Feb. 8.

About the 7-year-old Syrian girl who met Turkish President Recep Tayyip Erdogan on Wednesday and said she was happy to be evacuated from Aleppo but her dream would be to go back to her city one day, de Mistura said: "We all have the duty to make sure that she goes back not when she is a grown-up but as soon as possible to Aleppo.”

Praising the efforts of Turkish nongovernmental organizations to provide humanitarian assistance in Syria during the Aleppo evacuation operation, Egeland said: "IHH [Humanitarian Relief Foundation – a Turkish NGO] has done a great job."

Syria has been locked in a devastating civil war since early 2011, when the Bashar al-Assad regime cracked down on pro-democracy protests – which erupted as part of the Arab Spring uprisings – with unexpected ferocity.

Since then, more than a quarter of a million people have been killed and more than 10 million displaced across the war-battered country, according to the UN.

However, the Syrian Center for Policy Research, a Beirut-based nongovernmental organization, has put the total death toll from the five-year conflict at more than 470,000.